If $a + b = -10$ and $x + y = 5$, what is $-b - 2y - 2x - a$ ?
$= -a - b - 2x - 2y$ $= (-1) \cdot (a + b) + (-2) \cdot (x + y)$ $= (-1) \cdot (-10) + (-2) \cdot (5)$ $= 10 - 10$ $= 0$